John Ruth pointed to a company making molding plane irons:

http://www.corradishop.com/index.php?main_page=product_info&products_id=53

whose transcribed description includes:

"CORRADI GOLD molding plane irons are .... made using ledeburitic tool steel
which provides a high edge retention and reduced brittleness, thanks to a heat
treatment done according to the highest quality standards reached by Corradi
SpA?s century old manufacturing know-how...."
Does anyone know what ledeburitic tool steel" is? The term isn't in Wikipedia or
Wiktionary.
Tom Conroy